High frequency interference problem solution
High frequency plastic welding machine (hereinafter referred to as high frequency machine, Taiwan said high frequency, English Hing freguency plastic welder), often in different degrees affect nearby residents watch cable television, therefore, engineers discussed specific research, basically find out the characteristics of the high frequency machine for cable TV interference, at the same time for some cable to prevent and reduce the high frequency machine interference.
1.high frequency machine jamming signal spectrum analysis
High frequency machine has two types, 1) ordinary high-frequency machine (hereinafter referred to as the "PuTongJi"), is 4 kw - 150 - kw power. High-frequency machine outward radiation disturbance signal mainly has three parts: one is the iron plate on one side of the table at the bottom of the tube and the oscillation circuit, although there are two directions to seal on the sheet, but the other two directions is detachable door; Second is the high frequency feeder inside the workstation, processing mould and jig, this is one of the main parts of radiation; 3 it is below the workbench for the output of high frequency switch and capacitor, due to its close to the iron table and chassis shell plate and a very short lead, estimates that its radiation is weak. 2) tamper proof type high frequency machine, just install the high-frequency oscillating tube and the circuit in block within the circular iron drum, and other parts have not any block, although it has anti-jamming effect, but the effect is limited, we measured the intensity of the interference level is PuTongJi 75%, would still be on cable TV signal interference.
More than two types of high frequency machine are autonomous high-frequency oscillator, its characteristic is the power output tube itself is oscillating tube, therefore the frequency of the output is not a single, but a band, one of the frequency of the oscillation output the strongest known as the fundamental, the rest are called harmonics. The author measured three Ordinary machine base wave frequency is 32.50 MHz, respectively 32.80 MHz and 33.65 MHz. On both sides of the fundamental wave, harmonic distribution Ordinary machine total bands between 20 to 38 MHZ.
Use DS1240 field strength meter used for frequency spectrum analysis of the minimum can be analysed for 46 MHZ, unable to fundamental wave and harmonic signals of high-frequency machine group of spectrum analysis directly, we have to deal with the second harmonic frequency spectrum analysis. Because of the fundamental wave and harmonic intensity difference is too big, could not have a scan, all red points, high level and low level two scan, scan, according to the results of using ordinary TV in high frequency locomotive